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Lecture 1

BIO130 Lecture One Guide

9 Pages
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Department
Biology
Course Code
BIO130H1
Professor
Kenneth Yip

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Chapter 1 Cells and Genomes
(pg. 1 42)
The Universal Features of Cells on Earth
-All Cells Store Their Hereditary Information in DNA
-All Cells Replicate their Hereditary Information Through Templated
Polymerization
-All Cells Transcribe Portions of Their Hereditary Information into RNA
-All Cells Use Proteins as Catalysts
-All Cells Translate RNA into Protein the Same Way
-The Fragment of Genetic Information Corresponding to One Protein is One Gene
-Life Requires Free Energy
-All Cells Function as Biochemical Factories with the Same Basic Molecular
Building Blocks
-The same segment of DNA can be used repeatedly to guide the synthesis of many
identical RNA transcripts. Thus, whereas the cells archive of genetic information in
the form of DNA is fixed and sacrosanct, the RNA transcripts are mass-produced
and disposable
-The monomers of protein are amino acids and there are 20 types
oEach amino acid is built around the same core structure through which it can
be linked in a standard way to any other amino acid in the set; attached to
this core is a side group that gives each amino acid a distinctive chemical
character. Each of the protein molecules, or polypeptides, created by joining
amino acids in a particular sequence folds into a precise three-dimensional
form with reactive sites on its surface
-The information in the sequence of a mRNA molecule is read out in groups of three
nucleotides; what is called a codon
oThe code is read out by a special class of small RNA molecules; transfer
RNAs (tRNAs)
oEach type of tRNA becomes attached at one end to a specific amino acid, and
displays at its other end a specific sequence of three nucleotides—an
anticodonthat enables it to recognize, through base-pairing, a particular
codon or subset of codons in mRNA
oMany tRNAs reading and forming anticodons help form protein chain
-These processes are carried out on ribosomes, formed of two main chains of RNA,
called ribosomal RNAs, and more than 50 different proteins
-Ribosomes latch onto the end of an mRNA molecule and then moves along
it, capturing loaded tRNA molecules and stitching together the amino acids
they carry to form a new protein chain
SUMMARY: (mRNA to protein) (TRANSLATION)
oDNA is transcripted into mRNA
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oRibosomes slide across mRNA, reading each codon (translation
begins here)
otRNA carrying the correct amino acid will have the complementary
anti-codon necessary to bind to that codon on mRNA
othe amino acid then bonds with preceding amino acids creating a
chain
othis continues until a codon on mRNA signals STOP
-A gene is defined as the segment of DNA sequence corresponding to a single protein
or set of alternative protein variants (or to a single catalytic or structural RNA
molecule for those genes that produce RNA but not protein)
-In all cells, the expression of individual genes is regulated: instead of manufacturing
its full repertoire of possible proteins at full tilt all the time, the cell adjusts the rate
of transcription and translation of different genes independently, according to need
-the genome of the cellthat is, the total of its genetic information as embodied in
its complete DNA sequencedictates not only the nature of the cells proteins, but
also when and where they are to be made
Life Requires Free Energy
-to specify one bit of informationthat is, one yes/no choice between two equally
probable alternatives—costs a defined amount of free energy that can be calculated
-All cells, for example, require the phosphorylated nucleotide ATP (adenosine
triphosphate) as a building block for the synthesis of DNA and RNA; and all cells
also make and consume this molecule as a carrier of free energy and phosphate
groups to drive many other chemical reactions
All Cells are Enclosed in a Plasma Membrane Across Which Nutrients and Waste
Materials Must Pass
-The molecules forming this membrane are amphiphilic; both hydrophobic and
hydrophilic sides
-spontaneously aggregate in water to form a bilayer that creates small closed vesicles
(hydrophobic sides obviously pointed inwards)
-hydrophobic tails of the predominant membrane molecules in all cells are
hydrocarbon polymers
o(CH2CH2CH2)
-cells produce molecules whose chemical properties cause them to self-assemble into
the structures that a cell needs
-All cells have specialized proteins embedded in their membrane that transport raw
nutrients in, and waste out
A Living Cell Can Exist With Fewer Than 500 Genes
-bacterium Mycoplasma genitalium
-has only about 480 genes in its genome of 580,070 nucleotide pairs, representing
145,018 bytes of informationabout as much as it takes to record the text of one
chapter of this book
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-The minimum number of genes for a viable cell in todays environments is roughly
200–300, although there are only about 60 genes in the core set shared by all living
species
Summary
-The individual cell is the minimal self-reproducing unit
-Every cell on our planet stores its genetic information as double-stranded DNA
-The cell replicates its information by separating DNA strands and using each side as
a template for polymerization to make a new DNA strand with a complementary
sequence of nucleotides
-The same strategy of templated polymerization is used to transcribe portions of the
information from DNA into RNA
-RNA guide the synthesis of protein molecules using the ribosome (itself made of
RNA + protein)
-Proteins are the principal catalysts for almost all chemical reactions in the cell; their
other functions include the selective import and export of small molecules across the
plasma membrane that forms the cells boundary
-The function of each protein depends on its amino acid sequence, which is specified
by the nucleotide sequence of a corresponding segment of DNAthe gene that codes
for that protein
-In this way, the genome of the cell determines its chemistry; and the chemistry of
every living cell is fundamentally similar, because it must provide for the synthesis
of DNA, RNA, and protein
-The simplest known cells have just under 500 genes
The Diversity of Genomes and the Tree of Life
- Microorganisms make up most of the total mass of living matter on our planet
-Before we look at the tree of life, we need to consider the routes by which cells in
different environments obtain the matter and energy they require to survive and
proliferate, and the ways in which some classes of organisms depend on others for
their basic chemical needs
Cells Can Be Powered By a Variety of Free Energy Sources
-Trophe (Greek) food
-Organotrophic feed on other living things or organic chemicals they produce
-Phototrophic feeding on sunlight
oBacteria, algae, plants
oThe oxygen in our atmosphere is a by-product of their biosynthetic activities
-Lithotrophic feeding on rock (inorganic chemicals)
oBoth aerobic and anaerobic forms
oImportant when considering the history of the life of earth
Organotrophs could not exist without these primary energy converters (most
plentiful form of life)
-Hydrothermal vents found on the floor of the Atlantic and Pacific Ocean
-include H2S, H2, CO, Mn2+, Fe2+, Ni2+, CH2, NH4+, and phosphorus-containing
compounds
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Description
Chapter 1 Cells and Genomes (pg. 1 42) The Universal Features of Cells on Earth - All Cells Store Their Hereditary Information in DNA - All Cells Replicate their Hereditary Information Through Templated Polymerization - All Cells Transcribe Portions of Their Hereditary Information into RNA - All Cells Use Proteins as Catalysts - All Cells Translate RNA into Protein the Same Way - The Fragment of Genetic Information Corresponding to One Protein is One Gene - Life Requires Free Energy - All Cells Function as Biochemical Factories with the Same Basic Molecular Building Blocks - The same segment of DNA can be used repeatedly to guide the synthesis of many identical RNA transcripts. Thus, whereas the cells archive of genetic information in the form of DNA is fixed and sacrosanct, the RNA transcripts are mass-produced and disposable - The monomers of protein are amino acids and there are 20 types o Each amino acid is built around the same core structure through which it can be linked in a standard way to any other amino acid in the set; attached to this core is a side group that gives each amino acid a distinctive chemical character. Each of the protein molecules, or polypeptides, created by joining amino acids in a particular sequence folds into a precise three-dimensional form with reactive sites on its surface - The information in the sequence of a mRNA molecule is read out in groups of three nucleotides; what is called a codon o The code is read out by a special class of small RNA molecules; transfer RNAs (tRNAs) o Each type of tRNA becomes attached at one end to a specific amino acid, and displays at its other end a specific sequence of three nucleotidesan anticodonthat enables it to recognize, through base-pairing, a particular codon or subset of codons in mRNA o Many tRNAs reading and forming anticodons help form protein chain - These processesare carried out on ribosomes, formed of two main chains of RNA, called ribosomal RNAs, and more than 50 different proteins - Ribosomes latch onto the end of an mRNA molecule and then moves along it, capturing loaded tRNA molecules and stitching together the amino acids they carry to form a new protein chain SUMMARY: (mRNA to protein) (TRANSLATION) o DNA is transcripted into mRNA www.notesolution.com
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